The present invention relates generally to a method for detecting a fault, such as a clogged air filter, in a HVAC system.
A fault in an HVAC system can have a negative effect on the HVAC system. The fault can be a sensor failure, low refrigerant charge, and clogging of an air filter. An air filter is commonly used in an HVAC system to prevent airborne particles from entering an area that is being cooled. Over time, the air filter can clog and must be replaced. If the air filter is clogged, fan power consumption increases and system capacity decreases.
Additionally, the compressor can possibly fail, the life of the equipment can decrease, and the system may have to be taken temporarily out of service.
In prior systems, a sensor is employed to detect when the air filter is clogged. When the sensor detects that the air filter is clogged, an alarm is activated. There are several drawbacks to employing a sensor to detect a clogged air filter. For one, they are costly. Additionally, the design of the air filter may need to be modified to accommodate the sensors.
Other sensors are also generally utilized in the HVAC system to detect the pressure and the temperature of the refrigerant entering and exiting the compressor, the temperature of the refrigerant entering and exiting the evaporator, and the temperature of the air entering the evaporator.
Prior art fault detecting techniques are generally insensitive to variations in air concentration that occur when the air filter is clogged and the load of the system. Therefore, these techniques are only applicable to HVAC systems having a constant load that is supplied by a fixed speed fan.
Therefore, the present invention provides a method for detecting a fault in a HVAC system that overcomes the drawbacks and shortcomings of the prior art.